A delta-sigma modulation is a kind of oversampling modulation, and in general, is a technology used in AD conversion or DA conversion (see Non Patent Literature 1).
In delta-sigma modulation, noise shaping for greatly reducing quantization noise in a signal band by moving the quantization noise in the signal band to outside the signal band is performed.
Here, the term “delta-sigma modulation” means low pass delta-sigma modulation in many cases.
In low pass delta-sigma modulation, noise shaping is performed such that quantization noise at low frequencies is moved to higher frequency side, whereby quantization noise at low frequencies is attenuated. That is, in low pass delta-sigma modulation, a noise transfer function has a characteristic of stopping passing noise at low frequencies (near 0 Hz).
As delta-sigma modulation, other than the low pass delta-sigma modulation, there also is band pass delta-sigma modulation in which a noise transfer function stops passing noise at frequencies higher than 0 Hz.